Secondary emissive electronic discharge device



May 10, 1938. E. G. LINDER 2,117,098

SECONDARY EMISSIVE ELECTRONIC DISCHARGE DEVICE Filed April 30, 1936 2Sheets-Sheet 1 1 1 za T "325I /9 1 J 3nventor Erna-st 6-.L1lnder(Ittorneg May 10, 1938. E, G, UNDER 2,117,098

SECONDARY EMISSIVE ELECTRONIC DISCHARGE DEVICE Filed April 30, 1956 2Sheefs-Sheot 2 3nventor Ernest G.Linder (Ittorneg Patented May 10, 1938PATET OFFIQE SECONDARY EMISSIVE ELECTRONIC DIS- CHARGE DEVICE Ernest G.Linder, Philadelphia, Pa., assignor to Radio Corporation of America, acorporation of Delaware Application April 30,

8 Claims.

This invention relates to secondary emissive electronic dischargedevices and particularly to push pull electronic oscillators in whichthe electrons have appreciable transit times as compared to their periodof oscillation.

Ultra high frequency oscillators of the BarkhauseneKurtz or magnetrontype are well known to those skilled in the art. Such oscillators havedepended primarily upon electron emission from a heated cathode. Whilethe push pull electronic oscillator of this invention may employ aprimary electron source, such as a heated cathode or a photoemissiveelectrode, the main source of electronic oscillatory current is derivedby secondary emission of electrons. a

My invention may be most easily understood by reference to theaccompanying drawings, in which Fig. 1 is a schematic diagram of oneform of secondary emissive electronic oscillator,

. Fig. 2 represents a schematic illustration of a modified form ofoscillator,

Fig. 3 is a schematic diagram of a magnetron oscillator in which themain oscillatory current depends upon secondary emission,

Fig. 4 is a schematic representation of a magnetron oscillator which isa modification of Fig. 3,

Fig. 5 is a sketch illustrating the electronic paths of an oscillatorsimilar to the one illustrated in Fig. 3, and

Fig. 6 is a circuit diagram of an electronic device similar to Fig. 4but including a plurality of secondary emissive electrodes foramplifying the electronic currents.

Referring to Fig. 1, Within an evacuated en- 35 velope I are suitablysupported a cathode 3, an

apertured accelerating electrode 5 and a pair of secondaryemissiveelectrodes l, 9. This pair of electrodes '1, 9 are connected toa resonant circuit ll which may or may not be included 40 within theenvelope.

The cathode 3 may be energized by a battery I3. A pair of batteries 15,I! are serially connected between the accelerating electrode 5 and thecathode 3 to positively bias the former as 45 shown. A lead is isconnected between a point 2! intermediate the ends of the tuned circuitH and the junction of the serially connected batteries i5, H.

The operation of the circuit of Fig. 1 is essentially as follows:electrons emitted from the energized cathode 3, under the influence ofthe positively charged accelerating electrode 5 start toward theaccelerating electrode or anode. Some of these electrons strike theaccelerating electrode, while others pass through the apertures 23.

1936, Serial No. 77,144

The electrons passing through the apertures continue at high velocitiesand impinge upon the secondary emissive electrodes 1, 9. The primaryelectrons impinging on the emissive electrodes 7, 9 liberated increasingnumbers of secondary electrons, which flow to the accelerating anode.This action gives rise to a negative resistance characteristic.

Since one of the pair of emissive electrodes will be naturally slightlymore emissive than the other, one of the electrodes will becomemomentarily negative with respect to the other, thereby establishingtransient currents in the oscillator circuit II. The transient currentswill have an oscillatory frequency equal to the resonant frequency orperiod of the tuned circuit, which is preferably adjusted to equal thetime of transit of electrons moving from the accelerating electrode tothe secondary .emissive electrode.

In Fig. 2 the arrangement is as follows: Within an envelope 3| aresuitably mounted a primary emissive electrode 33, a grid-like accelerat-.ing electrode 35 substantially coaxially arranged with respect toprimary emission electrode, and a pair of secondary emissive electrodes31, 39. The secondary emissive electrodes are preferably semicylindricaland are joined by an oscillatory circuit 4|. The cathode 33 is energizedby a battery 43. The accelerating electrode 35 is positively biased withrespect to the cathode by a pair of serially connected batteries 45, 41.The emissive electrodes 37, 39 are positively biased by a connection 49from the junction of the serially connected batteries 55, 41 and a point5| intermediate the ends of the tuned circuit 4 I The operation of thecircuit of Fig. 2 is essentially the same as Fig. 1. Some of theelectrons leaving the cathode 33 pass through the meshes of theaccelerating electrode 35, and impinge on the emissive electrodes 31, 39thereby liberating secondary electrons, which flow to the acceleratingelectrode. A negative resistance characteristic starts the oscillatorycurrents which flow in the oscillatory circuit 4|. The oscillatoryfrequency is preferably related to the electron transit time, aspreviously described.

In Fig. 3, a modified electrode arrangement and also a magnetic fieldare employed. Within the envelope 6| are mounted a cathode 63, acylindrical accelerating anode 65 coaxially arranged with respect tosaid cathode, and a pair of secondary emissive electrodes 61, 69. Theemissive electrodes may each consist of a single wire or a plurality ofspaced wires arranged concentrically between the accelerating electrodeand cathode.

A magnetic field whose lines of force are nearly parallel to andsurround the cathode is established by a solenoid H (illustrated in cutaway form) which may be energized by a battery 13, or any suitablearrangement may be used to establish the magnetic field. The cathode 63is energized by a battery 15. The accelerating electrode 65 is biasedpositively by a pair of serially connected batteries ll, 19 which areconnected between the accelerating electrode and the cathode.

The secondary emissive electrodes 61, 69 are connected to the terminalsof a resonant circuit 8|. The junction of the serially connectedbatteries 71, 19 is connected to a point 83 intermediate the terminalsof the resonant circuit Bl. The operation of the foregoing circuitdiffers slightly from the circuits illustrated in Figs. 1 and 2. In thepresent circuit, the magnetic field causes the primary electrons emittedfrom the cathode to take spiral paths from the cathode 63 toward theaccelerating electrode 65. The field strength is adjusted tosubstantially cut-off with respect to the accelerating electrode.

Some of the electrons spiralling outwardly from the cathode will impingeupon the secondary emissive electrodes 67, 69 at high velocity. Theimpinging primary electrons will liberate secondary electrons which, inturn, spiral to the accelerating electrode. In Fig. 5 the paths of theprimary electrons are illustrated by the reference character P; whilethe paths of the secondary electrons are represented by S. The magneticfield is perpendicular to the plane of the illustration.

Negative resistance characteristics are established by the secondaryemission. By virtue of the negative resistance oscillatory currents areset up in the resonant circuit 8|. For optimum operation the electrontransit time between the cathode 63 and the secondary emissiveelectrodes 61, 69 should equal one oscillation period. The structure ofthe electronic tube of Fig. 3 contributes to low inter-electrodecapacities and enables ultra high "frequency oscillations to beestablished.

The circuit and elements of Fig. 4 being essentially the same as Fig. 3,similar reference characters will indicate similar elements in this andfollowing figures. In the present circuit, an end view of the electrontube is shown. The solenoid is omitted but the magnetic field isrepresented by an appropriate legend. The accelerating anode 65 is splitand the semi-cylindrical parts thereof are joined by a lead to form aresonant circuit 81.

The split anode decreases the capacity between the emissive electrodes.The resonant circuit between the split anode or accelerating electrodesmay be adjusted to favorably react upon the resonant circuit 8|connected to the emissive electrodes and thereby increase the efiiciencyof the oscillator.

The circuit of Fig. 6 is not unlike that of Figs. 3 and 4 with theaddition of a plurality of accelerating electrodes. The emissiveelectrodes 61, 69 are concentrically arranged with respect to thecathode 63. A plurality of grid-like secondary emissive electrodes 89are concentrically arranged about the cathode 63. These electrodes 89are made more positive with respect to cathode as their spacingtherefrom increases. A battery 9 I, or the like, may be used to bias theseveral emissive electrodes.

The magnetic field, represented by a circle and appropriate legend, isof such strength that the electrons liberated from each emissiveelectrode must impinge upon the next outer electrode before it can reachthe further removed electrodes. The several electrode potentials areeach adjusted to emit secondary electrons. Each successive emissiveelectrode increases the electron current which is thus amplified.

In each of the several electronic tubes the oscillatory circuit isarranged to act in pushpull arrangement by the negative resistancecharacteristic established by the secondary emission. The secondaryemissive electrodes have surfaces which are made secondary emissive bymeans of a silver surface which is first oxidized, and thereaftertreated with caesium. It should be understood that other suitablematerials and treatments may be used to make the several electrodessecondarily emissive. put, or load circuits, may be connected to theelectronic devices by any of the well known coupling means.

I claim as my invention:

1. In a device of the character described, a source of primaryelectrons, an accelerating electrode, means for biasing saidaccelerating electrode positively with respect to said source, a pair ofelectrodes having surfaces adapted to emit secondary electrons uponimpingement of said primary electrons, a source of potential for biasing said pair of electrodes positively with respect to said source ofprimary electrons and less positive than said accelerating electrode,and a resonant circuit connected between said pair of electrodes.

2. In a push pull electronic oscillator, a cathode, a cylindrical shapeaccelerating anode substantially co-axially arranged with respect tosaid cathode, means for biasing said anode positively with respect tosaid cathode, a pair of secondary emitting electrodes interposed in theelectron path between said cathode and anode, means for biasing saidpair of electrodes positively with respect to said cathode, and aresonant circuit connecting said pair of electrodes and having a timeperiod which is responsive to the transit time of secondary electronsmoving between said pair of electrodes and said anode.

3. In a push pull electronic oscillator a cathode, a grid-likeaccelerating anode substantially coaxially arranged with respect to saidcathode, and a pair of semi-cylindrically shaped electrodes, said pairof electrodes having surfaces so treated as to be highly secondarilyelectron emissive, means for biasing said anode positively with respectto said cathode, means for biasing said pair of electrodes positivelywith respect to said cathode and less positively than said anode, and aresonant circuit terminating in said pair of electrodes and energizedalmost entirely by high frequency currents generated by electronsemitted from said secondary emissive electrodes.

4. In a device of the character of claim 2 means for establishing amagnetic field whose lines of force surround and are substantiallyparallel to said cathode.

5. In a device of the character described, a cathode, a pair ofsemi-cylindrical shape accelerating anodes substantially c'oaxiallyarranged with respect to said cathode, means for biasing said anodespositively with respect to said cathode, a resonant circuit joining saidanodes, a pair of secondary emissive electrodes interposed in theelectron path between said cathode and anode, means for biasing saidpair of electrodes The input and outpositively with respect to saidcathode, and a second resonant circuit connecting said pair of emissiveelectrodes and having a time period which is of the order of the transittime of secondary electrons moving between said emissive electrodes andsaid anodes.

6. In a device of the character of claim 5, means for establishing amagnetic field whose lines of force are substantially parallel to saidcathode.

'7. In a device of the character described, a cathode,a pair ofsemi-cylindrical shape accelerating anodes, substantially coaxiallyarranged with respect to said cathode, a resonant circuit joining saidanodes, means for biasing said anodes positively with respect to saidcathode, a pair of secondary emissive electrodes interposed in theelectron path between said cathode and anodes, means for biasing saidpair of electrodes positively With respect to said cathode, a secondresonant circuit connecting said pair of emissive electrodes and havinga time period which is of the order of the transit time of secondaryelectrons moving between said emissive electrodes and said anodes, aplurality of grid-like accelerating electrodes disposed between saidaccelerating anodes, and said emissive electrodes, and coaxiallyarranged with respect to said cathode, and means for biasing saidplurality of grids positively with respect to said cathode.

8. In a device of the character described, a source of primaryelectrons, an accelerating electrode, means for biasing saidaccelerating electrode positively with respect to said source, a pair ofelectrodes having surfaces which have been so treated as to adapt themto emit secondary electrons upon impingement of said primary electrons,a source of potential for biasing said pair of electrodes positivelywith respect to said source of primary electrons and less positivelythan said accelerating electrode, and a resonant circuit connectedbetween said pair of electrodes.

ERNEST G. LINDER.

